The supplier of frequency converter braking unit reminds you that with the increasingly widespread application of frequency converters in industrial production, understanding the structure of frequency converters, the electrical characteristics of main components, and the role of some commonly used parameters, as well as their common faults, is becoming more and more important.
1、 Overcurrent
Overcurrent is the most frequent fault phenomenon in frequency converters. There are many reasons that can cause overcurrent in frequency converters, and the most common is the load. Overcurrent faults can be classified into the following situations:
1. When restarting, if the speed converter trips as soon as it accelerates, it indicates that the overcurrent is very serious, usually caused by load short circuit, mechanical component jamming, inverter module damage, or low motor torque.
2. After being powered on, it trips, which usually cannot be reset. The main reason is that the actuation circuit and current detection circuit are damaged.
3. When restarting, it does not trip immediately, but rather during acceleration. The main reason may be that the acceleration time is set too short, the current upper limit is set too low, or the torque compensation is set too high.
2、 Overvoltage
1. Overvoltage alarm usually occurs during shutdown, and the main reason may be that the deceleration time is too short or there are problems with the braking resistor and braking unit.
2. If there is a braking unit inside the frequency converter and a braking resistor is connected to the outside of the frequency converter, if the phenomenon of "OU" still occurs during the deceleration process of the frequency converter, it should be due to the failure to set the energy consumption braking selection parameters, improper selection of the braking resistor resistance value, or the braking unit not working. At this time, the heating condition of the braking resistor can be checked to determine.
3. If there is a braking unit and braking resistor connected externally to the frequency converter, the phenomenon of "OU" still occurs during the deceleration process of the frequency converter. It may be that the "OU" detection point of the frequency converter is lower than the working point of the braking unit. In this case, the working point of the braking unit should be adjusted, or the "OU" protection point of the frequency converter should be adjusted.
3、 Undervoltage
Undervoltage is caused by the main circuit voltage being too low, which may be due to power phase loss, an open circuit in one bridge arm of the rectifier circuit, damage to the internal current limiting switching circuit (unable to short-circuit the current limiting resistor during normal operation, resulting in a large voltage drop across the resistor and causing the voltage to be sent to the inverter circuit to be too low), and damage to the external voltage detection circuit can also cause undervoltage problems;
1. Damage to one of the rectifier bridges or abnormal operation of the three thyristors may lead to undervoltage faults;
2. The main circuit relay contactor is damaged or the main circuit relay or contactor does not engage due to control circuit issues. The voltage loss of the DC bus may lead to undervoltage on the charging resistor.
3. The voltage detection circuit has malfunctioned, resulting in undervoltage issues.
4、 Overheating
Overheating is a common fault of frequency converters, which may be caused by high ambient temperature, stalling of cooling fans, poor temperature sensors, or motor overheating.
1. The surrounding temperature is too high, especially in summer. For supporting customers, the frequency converter is often installed in the control cabinet. If the cooling conditions of the control cabinet cannot meet the requirements, it will cause the temperature inside the control cabinet to be too high and "overheated".
2. Axial flow fan is stuck or not running.
5、 Unbalanced output voltage
Unbalanced output voltage is generally manifested as unstable motor speed and shaking, and the main reasons may be:
1. The inverter module is broken, resulting in unbalanced three-phase output voltage;
2. The drive circuit of the frequency converter is damaged, causing an imbalance in the three-phase output voltage;
3. The output contactor is damaged, causing the motor to run in phase loss;
4. Poor contact of the output cable sometimes leads to phase loss in the motor;
6、 Overload
Overload is a common fault, and when overload occurs, it should be analyzed first whether it is motor overload or frequency converter overload. In general, due to the strong overload capacity of the motor, as long as the parameters of the frequency converter are set properly, the motor is not easily overloaded; For the overload alarm of the frequency converter, it is necessary to check whether the output voltage of the frequency converter is normal.